The purpose of this research is to document the effects of microwave radiation (MWR) on the auditory periphery. The basic mode of analysis is the examination of single unit discharge properties in the primary and secondary pathways of this system. Previous work in this laboratory and elsewhere has shown that this system is responsive to pulsed MWR; the mechanism, however, of this interaction remains to be clearly defined. The primary aims of this project include the derivation of a more complete, quantitative understanding of this MWR-auditory interaction, to investigate the underlying physical basis for this effect and to evaluate the general biological significance and hazard potential of these MWR effects. The principal animal used in this study is now adult mongrel cats, however, rat models are occasionally of value. The response of single auditory fibers and cells are recorded via glass micropipettes located in the eighth nerve and brain stem auditory nuclei. The subsequent response of the units to acoustic test stimuli and to pulsed MWR at 915 MHz are then determined. The capability of pulsed MWR to mask or reduce the apparent magnitude of subsequently applied acoustic stimuli is tested. The application of these data is the analysis of the potential biological hazard of pulsed MWR, the relationship of this auditory coupling and any potential hazard to current therapeutic utilization of MWR and the implications for a general increase in the level of population exposure to this form of energy.